The use of particulate filters in the exhaust gas aftertreatment of motor vehicles has become indispensable with respect to complying with increasingly more stringent emission standards. A particulate filter in the exhaust system of a diesel or gasoline engine of a motor vehicle filters the solids contained in the exhaust gas, in particular the soot, and stores them via embedding on the surface or in the interior of the walls of the particulate filter.
The solids embedded in the particulate filter increase the flow resistance and, therefore, the exhaust gas back pressure in the exhaust system, which impairs the engine performance and the fuel consumption of the motor vehicle.
In order to restore the filter efficiency and the exhaust gas back pressure to a suitable value, the particulate filter is regenerated as soon as a certain soot mass has become embedded. The regeneration of the filter is accomplished by burning the embedded particulates. For this purpose, a suitable starting temperature may be employed, which for gasoline particulate filters, may typically be approximately 600° C., as well as an excess of oxygen in the exhaust gas fed to the gasoline particulate filter.
Due to the high temperatures typically prevailing in the exhaust system of gasoline engines, it is possible that a regeneration of a gasoline particulate filter will spontaneously occur in the drive mode. For example, the regeneration can set in at temperatures in the exhaust system above 600° C. as a result of the driver lifting off the gas pedal, since, in this case, a supply of fuel to the internal combustion engine is briefly interrupted, and so the exhaust gas can contain an excess of oxygen, which promotes the burning of soot in the gasoline particulate filter.
When a particulate filter is greatly loaded with soot, there is a risk that an either spontaneously occurring or actively started regeneration of the particulate filter will generate so much exothermic heat that, due to the overheating, the particulate filter will undergo accelerated aging or can even become damaged. A damaged particulate filter can cause consequential damage to other components, in particular, in the engine and exhaust system. In addition, such events are stored in the on-board diagnostics. The presence of such memory entries can be signaled to the driver or can be detected in the workshop and, depending on the requirement of the relevant emission standard, can prompt a repair or a replacement of the particulate filter.
The inventors herein have recognized the above issues and provide systems and methods to at least partly address them. In one example, a method for protecting a diesel particulate filter from overheating and premature aging, wherein the diesel particulate filter is disposed in the exhaust system of a diesel engine of a motor vehicle, and wherein the motor vehicle has a self-control mode for the autonomous control of a drive mode of the motor vehicle, includes starting the self-control mode, starting or verifying a regeneration process of the diesel particulate filter with burning of the soot particulates adsorbed on the diesel particulate filter, monitoring a temperature of the diesel particulate filter and/or of the exhaust gas directed through the diesel particulate filter during the regeneration process, and responsive to a monitoring result of the monitoring, adjusting a control of the self-control mode of the motor vehicle.
The self-control mode and the regeneration process can be started in the method for protecting the diesel particulate filter from thermal overheating, which is carried out in the motor vehicle comprising a diesel engine and a diesel particulate filter. For example, it is possible to first wait for the self-control mode to be started, e.g., by the driver, and then, in the self-control mode, to start the regeneration process and monitor said regeneration process, for example, by the stated temperature measurements. It is also possible, for example, to begin or carry out the method for protecting the diesel particulate filter from thermal overheating after the regeneration process has started when the vehicle enters the self-control mode, wherein, in this case, the regeneration process is first verified, e.g., a check is carried out as to whether a regeneration process is already underway.
The control of the self-control mode can be adjusted on the basis of the monitoring results, for example, when predefined threshold values for the temperature of the diesel particulate filter or the exhaust gas emerging therefrom are reached.
If it is detected that a burning of soot in the diesel particulate filter is starting or has already intensified, the adjustment of the control can be directed, in particular, to bringing the oxygen concentration of the exhaust gas entering the diesel particulate filter to low values in order to reduce or interrupt the exothermic reaction resulting from the burning of the soot. Alternatively or additionally, the adjustment of the control can be directed to generating a sufficient exhaust gas volumetric flow rate, by which sufficient cooling of the diesel particulate filter during the regeneration can be achieved.
In another example a method for protecting a gasoline particulate filter from overheating and premature aging, wherein the gasoline particulate filter is disposed in an exhaust system of a gasoline engine of a motor vehicle, and wherein the motor vehicle has a self-control mode for autonomous control of a drive mode of the motor vehicle, includes starting the self-control mode, starting a regeneration process of the gasoline particulate filter with burning of the soot particulates adsorbed on the gasoline particulate filter, monitoring a temperature of the gasoline particulate filter and/or of the exhaust gas directed through the gasoline particulate filter during the regeneration process, and responsive to a monitoring result of the monitoring, adjusting a control of the self-control mode of the motor vehicle.
In this way, the regeneration process may be prepared (e.g., initiated) and/or controlled via adjusting of the self-control mode. The starting of the regeneration process can be prepared as often as necessary, e.g., by selecting an optimal speed and a suitable gear of the transmission, and can be initiated by a brief interruption of the gasoline supply, which can result in an excess of oxygen in the exhaust system at a high temperature and, therefore, can result in a commencement of the soot burning. This soot burning can then be monitored according to the method, for example, by monitoring the temperature of the gasoline particulate filter or the exhaust gas flowing out of said filter.
Similar to that stated above for the diesel particulate filter, the control of the self-control mode can be adjusted on the basis of the monitoring results, for example, when predefined threshold values for the temperature of the gasoline particulate filter or the exhaust gas emerging therefrom are reached.
If it is detected that a burning of particulates in the gasoline particulate filter is starting or has already intensified, the adjustment of the control can be directed, in particular, to bringing the oxygen concentration of the exhaust gas entering the gasoline particulate filter to low values in order to reduce or interrupt the exothermic reaction resulting from the burning of the soot. This can be achieved, for example, by supplying the gasoline engine with an essentially stoichiometric fuel-air mixture, which induces a combustion of the oxygen in the gasoline engine that is as complete as possible.
Alternatively or additionally, the adjustment of the control can be directed to generating a sufficient exhaust gas volumetric flow rate, by which sufficient cooling of the gasoline particulate filter during the regeneration can be achieved. Due to the high temperatures of the exhaust gas, this is effective only under certain conditions, however, specifically when the gasoline particulate filter temperature is higher than the exhaust gas temperature during the regeneration.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.